Stereocontrolled 5-Exo-Trig Cyclization of Imidoyl Radicals in the Synthesis of Substituted (Alkylthio)pyrrolines, Pyroglutamates, and Thiopyroglutamates
Stereocontrolled 5-Exo-Trig Cyclization of Imidoyl Radicals in the Synthesis of Substituted (Alkylthio)pyrrolines, Pyroglutamates, and Thiopyroglutamates
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DOI：
10.1021/jo00124a056
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发表时间：
1995-09
影响因子：
3.6
通讯作者：
M. Bachi;A. Melman
中科院分区：
文献类型：
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作者：
M. Bachi;A. Melman
使用NOE分配了15（82%）和16（7%）（见实验部分）。从这些数据中推断出其他手性化合物的相对构型。9假设在β-巯基乙醇/AIBN介导的环化中内酰胺的形成通过方案3中所示的自由基、极性和热步骤的顺序进行。这通过在NMR管（CeD 9，80 ℃）中在严格无水无氧条件下进行的反应中鉴定归属于中间体17的NMR信号得到证实（参见实验部分）。考虑到产物的非对映体纯度和所用的温和反应条件，我们预期使用对映体纯的α-氨基酸衍生物10将允许对映体选择性合成各种取代的（烷硫基）吡咯啉、吡咯谷氨酸酯和硫代吡咯谷氨酸酯。这些化合物含有硫代亚氨酸酯、酰胺等官能度，
15 (82%) 16 (7%) was assigned using NOE (see Experimental Section). From this data the relative configurations of the other chiral compounds were deduced. 9 It was postulated that lactam formation in the/3-mercaptoethanol/AIBN-mediated cyclizations proceeds through the sequence of radical, polar, and thermal steps shown in Scheme 3. 1 This was corroborated by identification of NMR signals attributed to intermediate 17 in a reaction performed in the NMR tube (CeD9, 80 C), under strictly anhydrous oxygen-free conditions (see Experimental Section).Compounds 6, 7, and 10 used in the cyclization reactions are highly functionalized derivatives of racemic-amino acids. In view of the diastereomeric purity of the products and the mild reaction conditions employed, we expect that the use of enantiomericallypure a-amino acid derivatives10 will allow the enantioselective synthe-sis of a variety of substituted (alkylthio) pyrrolines, py-roglutamates, and thiopyroglutamates. These com-pounds contain functionalities like thioimidate, amide,